Overview of recent HERMES results

16th Workshop on High Energy Spin Physics

Marukyan, Hrachya^1

AANL (Yerevan Physics Institute), Alikhanian Brs. 2, Yerevan

036, Armenia^1

关键词: Azimuthal modulation;    Bose-Einstein correlations;    Longitudinal momentum;    Multi-dimensional structure;    Semi-inclusive deep-inelastic scatterings;    Spin density matrix;    Transverse momentum distributions;    Transverse polarization;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/678/1/012038/pdf
DOI  :  10.1088/1742-6596/678/1/012038

来源: IOP

【 摘 要 】

An overview of more recent and important results from the HERMES experiment are presented in this paper. HERMES collected a wealth of data using the 27.6 GeV polarized HERA lepton beam and various polarized and unpolarized gaseous targets. This unique data set opens the door to the measurements of observables sensitive to the multidimensional structure of the nucleon. Among them are semi-inclusive deep-inelastic scattering measurements of azimuthal modulations sensitive to the transverse momentum distributions, such as the leading- twist Sivers and Collins distributions and distributions sensitive to the convolutions of the twist-2 and twist-3 functions. They all provide an information on the three-momentum-dependent quark distributions. Knowledge on the quark distribution as a function of longitudinal momentum and transverse position in impact-parameter space can be accessed, e.g., through exclusive ω - meson leptoproduction, particularly through the measurement of spin density matrix elements and the measurement of azimuthal modulations on transversely polarized proton target. The measurement of Bose-Einstein correlations of hadron pairs in quasi-real leptoproduction are also presented. The transverse polarization of Λ hyperons measured again in quasi-real leptoproduction regime are presented as well. Finally, the new analysis for the search on pentaquark at HERMES are mentioned.